Week 3 - Synaptic Transmission and Drugs Flashcards
What evidence lead Sherrington to conclude that transmission at a synapse is not the same as transmission along an axon?
Sherrington found that the velocity of conduction through a reflex arc was slower than the velocity of an action potential along an axon. Therefore, some delay must occur at the junction between one neuron and the next
What is the difference between temporal summation and spatial summation?
Temporal summation is the combined effect of quickly repeated stimulation at a single synapse. Spatial summation is the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron
What was Sherrington’s evidence for inhibition in the nervous system?
He found that a reflex that stimulates a flexor muscle prevents contraction of the extensor muscles of the same limb. He therefore inferred that an interneuron that excited motor neurons connected to the flexor muscle also inhibited the input to the extensors muscle
What is an EPSP?
Excitatory Postsynaptic Potential - is the change in the membrane voltage of a postsynaptic cell following the influx of positively charged ions into a cell (typically Sodium) as a result of the activation of ligand-sensitive channels. This results in a depolarisation of the postsynaptic cell, thus increasing the likelihood of action potential propagation. These excitatory synapses serve to increase excitability in neurons.
What is an IPSP?
Inhibitory Postsynaptic Potential - result from an influx of negative ions (chloride) into, to the efflux of positive ions (potassium) out of the postsynaptic cell. This results in cell hyperpolarisation and thus decreases the likelihood of action potential propagation, and therefore represent inhibitory synapses.
What ion gates in the membrane open during and EPSP?
Sodium gates
What ion gates in the membrane open during and IPSP?
Chloride or potassium gates
Can an inhibitory message flow along an axon?
No, only action potentials propagate along an axon. Inhibitory messages - IPSP’s - decay over time and distance.
How well did Sherrington’s inferences about synapses harmonise with Cajal’s conclusions about the anatomy of neurons?
A) The two conclusions supported each other
B) Sherrington’s conclusions were incompatible with Cajal’s conclusions
C) The two conclusions were irrelevant to each other
A) The two conclusions supported each other
Sherrington based his conclusions on what type of evidence?
A) Microscope examination of synapses
B) Results of injecting drugs into the spinal cord
C) Electrical recordings from inside neurons
D) Observations of reflexive responses
D) Observations of reflexive responses
Although one pinch did not cause a dog to flex its leg, a rapid sequence of pinches did. Sherrington cited this observation as: A) Temporal summation B) Spatial summation C) Inhibitory synapses D) Refractory period
A) Temporal summation
Although one pinch did not cause a dog to flex its leg, several simultaneous pinches at nearby locations did. Sherrington cited this observation as evidence for what? A) Temporal summation B) Spatial summation C) Inhibitory synapses D) Refractory period
B) Spatial summation
According to Sherrington, why do the extensor muscles of a leg relax when the flexor muscles contract?
A) Voluntary control by the cerebral cortex
B) Inhibitory connections in the spinal cord
C) Direct connections between the muscles themselves
D) Control by different chemical neurotransmitters
B) Inhibitory connections in the spinal cord
In the membrane of a neuron, what happens during an IPSP?
A) All the ion gates in the membrane close
B) The sodium gates open
C) The potassium or chloride gates open
D) All the ion gates in the membrane open
C) The potassium or chloride gates open
In what way were Sherrington’s conclusions important for psychology as well as neuroscience?
A) He demonstrated the importance of unconscious motivations
B) He demonstrated the importance of inhibition
C) He demonstrated the phenomenon of classical conditioning
D) He demonstrated the evolution of intelligence
B) He demonstrated the importance of inhibition
